yes, it's true. what I mean is that--speaking in terms of the unbundled model--I still personally don't use mastodon as my main reading app or writing app; it's more of a peripheral thing that I check periodically along with various other communities like on discord, slack etc
this is still at the hypothesis stage, but if you're using the unbundled model, I'm not sure that having federated communities necessarily matters. since the most important interop/decentralization there comes from using separate reading and writing apps. because federation comes with costs in terms of usability and development speed, it might be just as well to focus on traditional centralized communities.
(though I'd still lean towards things like forums and discord servers vs. traditional-looking social networks--you can think of social networks like large individual communities, but they don't perform the role as well).